1. Technical Field to which the Invention Belongs
The present invention relates to a binder resin composition for high-solid primer to be used for the purpose of protection or beautiful ornament of polyolefinic resins, for example, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, etc.
2. Prior Arts
Because of high productivity, broad freedom in design and many advantages such as light weight, antirust and shock resistance, plastics are used very frequently as materials of automotive parts, electric parts, building materials, food packaging films, etc. Above all, because of low price and many excellent properties such as moldability, chemical resistance, heat resistance, water resistance and good electrical characteristics, polyolefinic resins are used extensively as industrial materials, and are one of materials that the growth of demand is most expected in future.
Different from synthetic resins with polarity such as polyurethane resin, polyamide resin, acrylic resin and polyester resin, however, polyolefinic resins are nonpolar and crystalline, hence they have drawbacks of difficult painting and adhesion. For the painting and adhesion of such polyolefinic resins with difficult adherence, low chlorinated polyolefins with strong adherence to polyolefinic resins are used as binder resins.
For example, chlorinated polypropylene or chlorinated propylene-xcex1-olefin copolymer containing carboxylic acid and/or carboxylic anhydride (Japanese Unexamined Patent Publication Nos. Sho 57-36128 and Sho 59-166534, Japanese Patent Publication No. Sho 63-36624), composition having modified copolymer graft copolymerized with xcex1,xcex2-unsaturated vinyl monomer containing hydroxyl group onto styrenexe2x80xa2conjugated diene block copolymer followed by further chlorination as an essential component (Japanese Unexamined Patent Publication Nos. Hei 4-248845 and Hei 5-25405), composition having chlorinated product of graft modified styrene-isoprene block copolymer as an essential component (Japanese Unexamined Patent Publication No. Hei 5-25404), composition having chlorinated product of graft modified propylenexe2x80xa2ethylenexe2x80xa2xcex1-olefin random copolymer as an essential component (Japanese Unexamined Patent Publication Nos. Hei 5-112750 and Hei 5-112751), method for crosslinking carboxyl group-containing chlorinated polyolefin with epoxy resin (Japanese Patent Publication Nos. Sho 63-50381 and Hei 01-16414, Japanese Unexamined Patent Publication No. Hei 8-100032), composition having modified chlorinated polyolefin obtained by reacting carboxyl group-containing chlorinated polyolefin with low-molecular diol or low-molecular compound with hydroxyl group and amino group as an essential component (Japanese Unexamined Patent Publication Nos. Hei 7-247381 and Hei 7-247382), composition mixed carboxyl group-containing chlorinated polyolefin with acrylic modified chlorinated polyolefin (Japanese Unexamined Patent Publication No. Hei 10-158447), carboxyl group-containing chlorinated polyolefin with particular molecular weight distribution (Japanese Unexamined Patent Publication No. 2000-198807), etc. are proposed.
In recent years, volatile organic compounds (VOC) contained in paint and ink are desired to be reduced, since they become the source of air pollution. As one of reducing methods, high solidification of paint (primer) and ink can be considered.
However, if conventional compositions aforementioned are highly solidified, then the viscosity of primer increases because of too high molecular weight, making the spray painting impossible. Hence, they cannot be used as binder resins for high-solid primers.
For using these compositions as high-solid primers, a method for mixing low molecular weight alkyd resin, acrylic resin, polyester resin, polyurethane resin, etc. is considered. However, since these low molecular weight resins are liable to dissolve into gasohol (a mixed solution of gasoline with alcohol added with 10% lower alcohol such as methanol or ethanol to regular gasoline), they have drawbacks of decreasing gasohol resistance. Besides, the gasohol resistance is an index that becomes a criterion of solvent resistance and is measured by soaking a painted plate into gasohol to judge whether is good or poor by the time until the coated film peels off.
There, for solving said problem, the inventors proposed a binder resin composition for high-solid primer, characterized by containing carboxyl group-containing chlorinated polyolefin with particular molecular weight distribution and ketonic resin (Japanese Patent Application No. 2000-239697). This method was excellent in the gasohol resistance, but the high-octane gasohol resistance that uses a mixed solution of high-octane gasoline consisting of regular gasoline and toluene with alcohol could not be satisfied.
The invention provides a binder resin composition for high-solid primer excellent not only in the adherence and gasohol resistance, but also in the high-octane gasohol resistance, to be used for painting moldings, sheets, etc. of polyolefinic resin.
The primer composition of the invention to solve said subject is a binder resin composition for high-solid primer, characterized by formulating 10 to 200 parts by weight of (A-3) shown below to 100 parts by weight of a mixture of (A-1) with (A-2) shown below within a range of mixing ratio by weight of (A-1/A-2) of 90/10 to 50/50.
(A-1): Carboxyl group-containing chlorinated polyolefin graft copolymerized with 1 to 10% by weight of at least one kind of unsaturated carboxylic acid monomer selected from carboxylic acids and/or carboxylic anhydrides onto polyolefin (I), and then chlorinated to a chlorine content of 10 to 30% by weight, the carboxyl group-containing chlorinated polyolefin (II) having not more than 2% by weight of component with weight average molecular weight of 2,000 being low-molecular weight region of said carboxyl group-containing chlorinated polyolefin and ratio (Mw/Mn) of weight average molecular weight (Mw) to number aver-age molecular weight (Mn) of 1.5 to 3.5.
(A-2): Ketonic resin with number average molecular weight of 500 to 2,000.
(A-3): Combination of one set or two or more sets selected from alcoxylated melamine and carbamate group-containing compound, alcoxylated melamine and hydroxyl group-containing compound, and isocyanate group-containing compound and hydroxyl group-containing compound.
In following, the invention will be explained in detail.
In the invention, (A-1) and (A-2) form the skeleton of binder resin. (A-1) is a component to provide the adherence to polyolefin and (A-2) is a low-molecular weight component indispensable for high solidification. (A-3) is a component that causes the crosslinking reaction when baking upper paint and is used for improved high-octane gasohol resistance.
Explanation on (A-1)
The carboxyl group-containing chlorinated polyolefin (II) to be used in the invention can be obtained by melting polyolefin (I) under heating, decreasing viscosity or degrading it through thermal decomposition, if need be, graft copolymerizing with unsaturated carboxylic acid monomer of carboxylic acid and/or carboxylic anhydride onto it batchwise or continuously in the presence of radical generator, and then chlorinating. Also, it can be obtained by dissolving polyolefin (I) into sol-vent at 100xc2x0 C. or higher in a reactor equipped with stirrer or autoclave, graft copolymerizing with unsaturated carboxylic acid monomer in solution in the presence of radical generator, and then chlorinating.
For the raw material polyolefins (I), crystalline polypropylene, noncrystalline polypropylene, propylene-xcex1-olefin copolymer, etc. can be used solely or by mixing two or more kinds. In particular, from the points of workability and adhesiveness of binder resin, crystalline polypropylene with weight average molecular weight of 10,000 to 150,000, propylene-xcex1-olefin copolymer with weight average molecular weight of 10,000 to 150,000 containing 70 to 97 mol % of propylene component, the number of carbons of xcex1-olefin being 2 or 4 to 6, or ternary copolymer of propylene-butene-ethylene with weight average molecular weight of 10,000 to 150,000 containing 70 to 97 mol % of propylene component, 2 to 25 mol % of butene component and 2 to 25 mol % of ethylene component is preferable. In the case of propylene-xcex1-olefin copolymer, xcex1-olefin unit is preferable to be at least one kind of xcex1-olefin with number of carbons of 2 or 4 to 6, selected from, for example, ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene and 1-hexene.
If the weight average molecular weight of raw material polyolefin (I) is under 10,000 or the propylene component is under 70 mol %, then the adherence to polyolefinic resin, gasoline resistance, heat resistance and ultraviolet resistance are aggravated. If the weight average molecular weight is over 150,000, then the primer does not become fine particles when painting by air spray etc. and the beautiful appearance is spoiled, which is unpreferable. Also, the number of carbons of a-olefin in propylene-xcex1-olefin copolymer is over 6, then the adherence to polyolefinic resin becomes poor. Moreover, the propylene content of propylene-butene-ethylene copolymer being ternary copolymer is preferable to be 70 to 97 mol % as described above, the butene content is preferable to be 2 to 25 mol % and the ethylene content is preferable to be 2 to 25 mol %.
Unsaturated carboxylic acid monomers capable of being used for introducing carboxyl group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, aconitic acid and aconitic anhydride. These can be used for graft copolymerization at a level of 1 to 10% by weight to polyolefin. If under 1% by weight, then the gasohol property is aggravated. If over 10% by weight, then the adherence to polyolefinic resin is aggravated and, at the same time, increased viscosity of solution due to hydrogen bonding is seen, resulting in gelation on preservation or poor workability by air spray etc.
The radical generators to be used for the graft copolymerization between polyolefin (I) and unsaturated carboxylic acid monomer include, for example, peroxides such as di-tert-butyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxide benzoate, methyl ethyl ketone peroxide and di-tert-butyl perphthalate, and azonitriles such as azobisisobutyronitrile.
The carboxyl group-containing chlorinated polyolefin (II) to be used in the invention can be used at a chlorine content of 10 to 30% by weight. If the chlorine content is under 10% by weight, then the solubility into organic solvents such as toluene and xylene is poor and homogeneous solution cannot be obtained, resulting in the gelation at low temperature or generation of grains, making it impossible to apply to binder resin for primer or base coating. If the chlorine content is over 30% by weight, then the adherence to polyolefinic resin and the gasoline resistance are aggravated, which is unpreferable.
The less the component in the low-molecular weight region of carboxyl group-containing chlorinated polyolefin (II) to be used in the invention, the better the heat resistance, ultra-violet resistance and gasohol resistance. That is, if the component with weight average molecular weight of 2,000 or less is contained over 2% by weight, then these physical properties are aggravated remarkably. Moreover, the carboxyl group-containing chlorinated polyolefin (II) can be used at a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), that is, the value of Mw/Mn of 1.5 to 3.5. If Mw/Mn is under 1.5, then the adherence to polyolefin becomes poor, and, when it exceeds 3.5 by increasing the component in high-molecular weight region, the high solidification becomes difficult. Also, when painting by air spray etc., the primer does not become fine particles and the beautiful appearance of coated surface is spoiled, which is unpreferable. When it exceeds 3.5 by increasing the component in low-molecular weight region, the heat resistance, ultraviolet resistance and gasoline resistance are aggravated.
Besides, the content of low-molecular weight component with weight average molecular weight of 2,000 or less and the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), that is, Mw/Mn were determined by means of gel permeation chromatography (GPC) using polystyrene with known molecular weight and narrow molecular weight distribution as a standard substance.
The carboxyl group-containing chlorinated polyolefin (II) to be used in the invention can be obtained by completely dissolving polyolefin graft copolymerized with unsaturated carboxylic acid under warming into solvents for chlorinating reaction, for example, chloroform, carbon tetrachloride, tetrachloroethylene, tetrachloroethane, etc., and then by blowing-in chlorine gas for reacting under pressure or ambient pressure in the presence of radical generator as described above, or under irradiation of ultraviolet rays, or in the absence of these radical generator and ultraviolet rays. The chlorinating reaction is conducted ordinarily at a temperature between 60xc2x0 C. and 120xc2x0 C.
As the methods for removing low-molecular weight component of carboxyl group-containing chlorinated polyolefin (II), two ways of (1) a method for removing low-molecular weight component in carboxyl group-containing polyolefin before chlorination by extracting with solvent, and (2) a method for removing low-molecular weight component in carboxyl group-containing chlorinated polyolefin after chlorination by extracting with solvent can be proposed.
For removing the low-molecular weight component by the method (1), carboxyl group-containing polyolefin before chlorination is made powery, granular, pelletal or molten state, sole solvent or mixed solvent selected from a group of aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon, halogenated hydrocarbon, alcohols, esters, ketones and ethers with boiling point of 120xc2x0 C. or lower is added, and the low-molecular weight component is dissolved out into these solvents within a temperature range of 10 to 100xc2x0 C., thereby it can be removed. Moreover, in the case of carboxyl group-containing polyolefin obtained by dissolving polyolefin (I) into solvent at 100xc2x0 C. or higher in a reactor equipped with stirrer or autoclave and graft copolymerizing with unsaturated carboxylic acid monomer in solution in the presence of radical generator, the reaction liquor is put in said solvent as it is and the precipitates are filtered, thereby the low-molecular weight component can be removed.
The reason why the boiling point of solvent was made to be 120xc2x0 C. or lower is because of that, if the boiling point id too high, the low-molecular weight component is liable to remain in the carboxyl group-containing polyolefin or carboxyl group-containing chlorinated polyolefin, and said solvent is chlorinated or the physical properties of primer are decreased, which is unpreferable.
The reason why the temperature on extraction was made to be 10 to 100xc2x0 C. is because of that, if under 10xc2x0 C., then the removal of low-molecular weight component by extraction becomes incomplete, which is unpreferable. Also, if over 100xc2x0 C., even the high-molecular weight component is removed and the recovery rate decreases, which is unpreferable. When using the solvent with boiling point of 100xc2x0 C. or lower, it is preferable to perform the solvent extraction in a completely closed pressure vessel.
The method for removing the low-molecular weight component by the method (2) is also possible following the method (1) using carboxyl group-containing chlorinated polyolefin. In the case of carboxyl group-containing chlorinated polyolefin being in solution, the temperature on extraction is preferable to be as low as possible. If under 0xc2x0 C., however, the viscosity becomes too high, hence the solvent extraction of low-molecular weight component cannot be performed efficiently. Also, if becoming higher than room temperature, the carboxyl group-containing chlorinated polyolefin dissolves into extracting solvent in large quantities and the recovery rate decreases, which is unpreferable. In the case of carboxyl group-containing chlorinated polyolefin being solid article, the extracting temperature is preferable to be higher, but, if over 100xc2x0 C., dehydrochloric acid etc. are caused to become unstable, which is unpreferable.
As the representatives of solvents with boiling point of 120xc2x0 C. or lower for removing the low-molecular weight component, in the case of aliphatic hydrocarbon, pentane, 2-methylpentane, hexane, 2,2-dimethylbutane, 2,3-dimethylbutane, heptane, 2-methylhexane, 3-methylhexane, 2,4-dimethylpentane, petroleum ether, petroleum benzine, etc. can be exemplified. In the case of aromatic hydrocarbon, benzene, toluene, etc. can be exemplified. In the case of alicyclic hydrocarbon, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, etc. can be exemplified. In the case of halogenated hydrocarbon, trichloromethane, tetrachloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, etc. can be exemplified. In the case of alcohols, methanol, ethanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 2-pentanol, 3-pentanol, etc. can be exemplified. In the case of esters, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, isobutyl acetate, sec-butyl acetate, etc. can be exemplified. In the case of ketones, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, methyl isobutyl ketone, etc. can be exemplified. In the case of ethers, diethyl ether, dipropyl ether, diisopropyl ether, etc. can be exemplified.
Explanation on (A-2)
For the ketonic resins with number average molecular weight of 500 to 2000 to be used in the invention, polycondensation products obtainable by condensing ketones (cyclohexanone, methylcyclohexanone, acetophenone, etc.) with formaldehyde can be used. In addition, those hydrogenated the ketonic portion obtained can also be used. The properties of resin differ depending on the type of raw material ketone and molecular weight of resin, but it is a faintly colored solid resin with softening point of around 70 to 120xc2x0 C. and has features of excel-lent weather resistance, adherence, hardness, etc.
Said ketonic resin can be used within a range of number average molecular weight of 500 to 2000. If the number average molecular weight is under 500, then the cohesion is poor and the adherence is aggravated. If over 2000, the high solidification of primer becomes difficult.
Besides, the number average molecular weight is a value determined by means of gel permeation chromatography (GPC) using polystyrene with known molecular weight and narrow molecular weight distribution aforementioned as a standard substance.
Explanation on (A-3)
Alcoxylated melamine to be used in the invention can be obtained by publicly known methods (e.g. Handbook of Paint, p.224-230, 1965, published by The Nikkan Kogyo Shimbun Ltd., etc.). Melamine and formaldehyde are reacted under warming to produce methylolmelamine. Then, by reacting this with alcohol, alcoxylated melamine can be obtained. Typically, methylated methylolmelamine, butylated methylolmelamine, isobutylated methylolmelamine, etc. can be mentioned. Moreover, commercial products such as Melan (trade mark, from Hitachi Chemical Co., Ltd.) and Super Beckamine (trade mark, from Dainippon ink and Chemicals, Inc.) can also be used. Carbamate group-containing compound is a compound having carbamate group (xe2x80x94Oxe2x80x94COxe2x80x94NHR, Rxe2x95x90H or alkyl (preferably alkyl with number of carbons of 1 to 6 or cycloalkyl with number of ring carbon atoms of up to 6), and, in particular, H is preferable). Compounds such as carbamate-based poly(meth)acrylics copolymerized isocyanate-based monomer with unsaturated group with (meth) acrylic monomer etc. and carbamate-based oligomer obtainable through following reaction formulae can be used, if they have two or more carbamate groups in one molecule. Moreover, compounds obtainable by other publicly known methods (e.g. Japanese Unexamined Patent Publication No. Hei 8-231642, U.S. Pat. Nos. 3,479,328, 3,674,838, 4,126,747, 4,279,833, 4,340,497, 4,758,632 and 5,356,669, P. Adams and F. Baron, xe2x80x9cEsters of Carbamic Acidxe2x80x9d, Chemical Review, v65, 1965, etc.) can also be used.
[Chemical Formula 1]
Hydroxyl group-containing compounds include high-molecular polyols such as acrylic polyol, polyester polyol and polyether polyol, alkyd resins, and liquid rubber and liquid polybutadiene with hydroxyl groups at both ends of molecule, etc. In addition, hydrogenated liquid rubber and hydrogenated liquid polybutadiene with hydrogens added to double bonds in said liquid rubber and liquid polybutadiene, etc. can be used, if they are compounds with two or more hydroxyl groups in one molecule.
Isocyanate group-containing compounds mean aromatic, aliphatic and alicyclic organic diisocyanates and include, for example, tolylenediisocyanate, xylenediisocyanate, 1,5-naphthalenediisocyanate, 1,4-tetramethylenediisocyanate, 1,6-hexamethylenediisocyanate, 2,2,4-trimethylhexamethylenediisocyanate, isophoronediisocyanate, 4,4-dicyclohexylmethanediisocyanate and 1,4-cyclohexyldiisocyanate. Moreover, it may also be safe to modify these organic diisocyanates to isocyanate derivatives such as burette form, isocyanurate form and trimethylolpropane adduct form for use, hence all compounds can be used, if they have two or more isocyanate groups in one molecule. Furthermore, block isocyanate compounds blocked said isocyanates with blocking agent can be used. The blocking agents include, for example, oximes such as methyl ethyl ketoxime, cyclohexanone oxime, formaldoxime and acetoaldoxime, phenolics such as phenol and cresol, alcoholics such as methanol, benzyl alcohol and ethyleneglycol monomethyl ether, active methylenes such as methyl acetoacetate and dimethyl malonate, amides such as acetanilide and acetamide, other imides, amines, imidazoles, ureas, carbamates, imines, mercaptans, sulfites and lactams.
Among said compounds, mixture of alcoxylated melamine with carbamate group-containing compound, mixture of alcoxylated melamine with hydroxyl group-containing compound, mixture of isocyanate group-containing compound with hydroxyl group-containing compound, etc. can be used. As for the mixing ratio of respective compounds, effect can be recognized at an arbitrary mixing ratio, but, preferably, the mixing ratio is within a range of 2/8 to 8/2 by solid weight. These mixtures can be used plurally.
Moreover, for the purpose of promoting the reaction between alcoxylated melamine and carbamate group-containing compound, or alcoxylated melamine and hydroxyl group-containing compound, acidic catalysts such as hydrochloric acid, nitric acid, phosphoric acid and organic acid can be used. For example, they are alcohol solution of hydrochloric acid, salts of strong acid such as ammonium chloride, phosphoric esters such as monobutyl phosphate, organic sulfonic acids such as p-toluenesulfonic acid, etc., and these can be used solely or by mixing two or more kinds.
In the invention, the mixing ratio by weight of (A-1)/(A-2) is within a range of 90/10 to 50/50. In said mixing system, if (A-1) is under 50, then the adherence to polyolefinic substrate and the gasohol resistance are aggravated. If (A-1) is over 90, then the high solidification becomes difficult.
Moreover, to 100 parts by weight of mixture with mixing ratio by weight of (A-1)/(A-2) within a range of 90/10 to 50/50, the optimum formulating proportion of (A-3) is 10 to 200 parts by weight. If under 10 parts by weight, the gasohol resistance does not improve. If over 200 parts by weight, then the adherence to polyolefinic substrate becomes poor, which is unpreferable.
To the inventive binder resin composition for high-solid primer, titanium dioxide, talc, coloring pigment, etc. are added within a range not injuring the effect of the invention, and, if need be, other additives, for example, ultraviolet absorber, antioxidant, sedimentation preventer for pigment, etc. are added and kneaded, thereby the high-solid type primer can be produced.